Induction heating device for rod and tube-shaped material



y 1962 w. ROSSNER 3,035,142

INDUCTION HEATING DEVICE FOR ROD AND TUBE-SHAPED MATERIAL Filed April 20, 1960 4 SheetsSheet 1 W. RQSSNER May 15, 1962 INDUCTION HEATING DEVICE FOR ROD AND TUBE-SHAPED MATERIAL Filed April 20; 1960 4 Sheets-Sheet 2 W. RCSSNER May 15, 1962 INDUCTION HEATING DEVICE FOR ROD AND TUBE-SHAPED MATERIAL 4 Sheets-$heet 3 Filed April 20, 1960 Fig. 4

y 15, 1962 w. RassNER 3,035,142

INDUCTION HEATING DEVICE FOR ROD AND TUBE-SHAPED MATERIAL Filed April 20, 1960 4 Sheets$heet 4 3,035,142 INDUCTIGN HEATING DEVICE FOR ROD AND TUBE-SHAPED MATERIAL Wolfgang Riissner, Nurnberg, Germany, assignor to Siemens-Sehuckertwerke Aktiengesellschaft, Berlin-Siemensstadt, Germany, a corporation of Germany Filed Apr. 20, 1960, Ser. No. 23,407 Claims priority, application Germany Apr. 21, 1959 9 Claims. (Cl. 2199.5)

My invention relates to a device for heating rod or tube material in electric soldering, brazing, welding, melting and other heat processing operations, including floating zone, crucible-free single crystal semiconductor processes.

The heating of rod and tube material by electric induction is often preferred to other heating methods because it permits a uniform and locally very limited heating of the material. The required induction or glow coils can be given a relatively simple design. Difficulty is encountered when the material to be heated is of ex tremely high quality and must not be oxidized nor contaminated, by the heating, a requirement to be met for example with metals and other materials to be used in nuclear reactor techniques. As a rule, such material is heated in sealed chambers that are filled with protective gas. The gas consumption is rather high and there may also be the danger of explosion. In some cases, it is also necessary to clean the processing space by evacuation before supplying it with the protective gas, or to operate entirely in vacuum. Such devices are expensive and difficult to service. In lieu of a vacuum, an inert protective gas such as argon may also be used. However, since the processing chambers must be evacuated rather a relatively long time prior to performing the heating process proper, or must be scavenged with the inert gas prior to the heating operation to a sufiicient extent to eliminate any residual trace of air, the design and operation of such a device involves an unsatisfactorily great expenditure or gas consumption.

It is an object of my invention to avoid these disadvantages and to devise processing equipment of simple design which combines readiness for a quick heating operation with easy servicing requirements and minimized gas consumption.

According to a feature of my invention, which particularly relates to an induction device for heating electrically conducting material, such as rods or tubes, under inert or active protective gas, in soldering, welding, melting and other similar operations, the active range of the induction heater is located within a processing space that is surrounded bya tubular and double-walled body whose inner wall possesses pores for the passage of the protective gas.

These and more specific features of my invention, as Well as the objects pursued and the advantages achieved thereby, will be apparent from the following description made in conjunction with the accompanying drawings, in which a number of exemplary embodiments of devices according to the invention are illustrated.

FIG. 1 is an axial sectional view of a device for soldering a tubular sleeve, such as one used, for example, as or for a nuclear fuel element of a nuclear reactor.

FIG. 2 is a corresponding sectional view of a modified soldering device, and

FIG. 2a is a top view of the appertaining inductionheater coil proper, located in the plane denoted by AB in FIG. 2.

FIG. 3 is a lateral view in axial section, of a third embodiment applicable for the soldering or other heat processing of rod or tube material.

FIG. 4 is a lateral, sectional view of a further modification, and

FIG. 4a is a cross-section along the plane denoted by A-B in FIG. 4.

FIG. 5 shows a lateral, sectional view of another modified device.

FIG. 5a is a cross-section along the plane denoted by 5a in FIG. 5.

Similar reference numerals are employed in the illustrations to denote corresponding components.

In the induction heater of FIG. 1, a reactor fuel-element sleeve 1 of metal and a metallic end piece 2 are to be joined by soldering. The ends of the two parts are telescoped or stuck together so as to form an annular groove in which a ring 15 of solder material is located. A weight 22 serves to maintain the two parts 1, 2 under pressure so that when the material 15 becomes liquid during the soldering operation, an accurate fitting of the two parts is secured. The solder junction is located within an inductance coil 3 comprising two winding turns and consisting of a tube which is traversed by cooling water during operation. The induction coil 3 is located Within a processing chamber which includes or is designed as a device for supplying a protective gaseous atmosphere, and is fastened to that device by means of clamps 6 and 7. The gas is supplied to the processing chamber from an annular interstitial chamber 411 formed between an inner porous cylinder 4 and an outer concentric jacket cylinder 5. The interstitial space 4a communicates with a hose nipple 9 for supplying the protective gas. The annular chamber 4 is closed above and below by ring shaped cover plates 23 and 23a which are rigidly and tightly joined with the two cylinders 4 and 5, for example by soldering. A pipe 10, located coaxially within the reactor fuel-element sleeve member 1, provides the inner space of that member with protective gas in order to avoid corrosion or oxidation of the inner surfaces of the structure being soldered.

During the soldering operation, the protective gas is supplied through nipple 9 into the annular space 4a from which it passes through the uniformly distributed pores of the inner cylinder 4 into the processing space where it provides turbulence-free or whirl-free displacement of any amounts of residual air that may be located in this space. Depending upon the particular requirements, the protective gas may be composed of any of the conventional substances. For example, it may consist of an active protective gas, such as hydrogen, or an inert protective gas, such as nitrogen or argon, depending upon the materials being processed.

It is preferable to keep the diameter of the inner porous cylinder 4 as small as feasible. This condition is readily satisfied with electrically non-conductive porous cylinders but may involve difliculty when employing porous cylinders that consist of metallic material, such as a body of sintered metal. In the latter case, it is best to take care that no ferromagnetic material is being used, and that the space between the inductor coil and the outer wall is at least-three times as large as the spacing between the coil and the workpiece. This expedient is necessary where it is desired to reduce eddy currents in the metallic porous cylinder to a small value permissible from the heat technology viewpoint. However, the formation of eddy currents can also be minimized by special expedients such as the provision of slits 4b along the generatrix lines of the cylinder 4, and the filling of the slits with an insulating material. The slits may also be given such an orientation that they interlock the normally occurring flow lines of the eddy currents. If a suflicient power supply is available, it is also possible to keep the spacing between the components narrower than stated above, and to dis- .4 and .5 of the soldering device proper.

sipate the resulting heat losses with the aid of additional or supplemental water cooling.

During operation electric voltage is applied to the tubular conductors 3a and 3b of the induction coil 3, while the tubular conductor, including the coil 3, is traversed by cooling water, as indicated by arrows Be and 3 To facilitate assembling and installing the device, the connection of conductor 3b with coil 3 is interrupted at 30 and the two conductor portions are connected with each other by piece 8 of elastic non-conducting hose so that the cooling water can pass through the conductor and coil. Due to the interruption of the electric conductor at 30, the operating current for the coil 3 passes at clamp 6 iirom the tubular conductor 3b to the jacket of the device whence it flows through clamp 7 to the conductor coil 3.

In the device illustrated in FIGS. 2 and 2a, the induction heating coil 30 has only one winding turn and is embedded in the inner porous cylinder 40 which in this embodiment consists of non-metallic, preferably ceramic, material. Outer shell 50 is similar to wall 5 of FIG. 1. For embedding the inductor coil, the cylinder 40 can preferably be made of two half-portions (not shown) which enclose the coil '3 from above and below. The fiurther design of the protective-gas supply device is essentially the same as described above with reference to FIG. '1, except that the ring-shaped interstitial chamber 4a is covered at the top by a cover plate 11 whose central opening 11a is smaller than the diameter of the processing chamber formed by the cylinder 40. The central opening 11a preferably has a cross-section adapted to the crosssectional shape of the workpiece. The opening 11a may also be shaped to form a guide for the workpiece as it is being placed axially into the processing space. The cover plate 11 may consist of a similar material as the inner cylinder 40, for example, ceramic material. Due to the small size of the opening 11a, the flow cross-section for the protective gas passing out of the chamber is reduced so that a smaller quantity of protective gas is sufficient. In this respect, the device can he further improved by also closing the bottom of the processing chamber by a cover plate whose central opening is not larger than required for the convenient passage of the workpiece. The cover plate 11, and if desired also a corresponding cover plate at the bottom of the device, may also serve to facilitate centering or guiding the workpiece for example when the workpiece is being preheated while it is being fed into the processing space. Inner porous cylinder 40 may be wholly or partially of non-conductive ceramic material or non-conducting metal oxide or synthetic material. The porous portion, particularly, is non-conducting.

In the embodiment shown in FIG. 3, the above described upper cover plate 11 is replaced by an additional protective gas chamber comprising a porous inner cylinder '12 and a concentric outer jacket cylinder 13. The two cylinders form an interstitial, annular space 12a in addition to the annular space 4a between the cylinders The annular chamber 12a 'is supplied with protective gas through-a connecting conduit 14 from the annular chamber 4a. The

purpose of the additional protective-gas device is to cool to any desired heat processing, soldering for example,

while the tube is being gradually fed upwardly through the device.

In the embodiment so far described, the inductor and the protective-gas device are essentially separate structural elements. However, both can be more closely combined with each other as is apparent from the device shown in FIGS. 4 and 4a.

In this device, the inductance coil described above is replaced by a concentrator comprising a primary winding 3 and the concentrator winding 16-- 16 proper. Both are separated from each other by an electrically insulating layer 17. The primary winding consists of a water-cooled copper tube 30'. The concentrator winding has an inner disc 16, in its middle and having a bore concentrically surrounding the workpiece duiing the operation. The entire body of the concentrator winding 16--16 is provided with a slit 19 on one side. As far as described, the device, comprising the primary winding and the concentrator structure is known as such. According to the present invention, such a device is modified by the insertion of two coaxial porous cylinders 41 and 42 located in alignment with each other on opposite sides of the center disc flange 16, which is preferably integral with concentrator tube 16. The two porous cylinders 41 and 42 form, together with the outer jacket portion 16 of the concentrator, two interstitial annular chambers 4d and 4e. The protective gas is supplied to the two annular chambers 4d, 4e through respective conduits 9a and 9b which are both joined to a gas nipple 9. The annular chambers 4d and 4e are covered by upper plate 18 and lower plate 18" whose center bores may be sufficiently smaller to carry out the purpose of limiting the gas consumption, as described above with reference to FIG. 2. It is preferable to make the porous cylinders 41 and 42 of electrically insulating, for example ceramic, material in order to further minimize eddy current losses which by virtue of the slitted design are a lready kept within relatively small limits. The concentrator windings 1616 are of electro-conductive material. An embodiment of the type shown in FIGS. 4 and 4a affords a favorable and economical application of high-frequency alternating currents that can be con- .centrated in the described manner, for the purpose of heating conducting material under a protective-gas atmos- .phere.

FIGS. 5 and 5a illustrate a protective-gas device in combination with a concentrator, generally of the type described above with reference to FIGS. 4, 4a, which facilitates the concentrated application of extremely high energy density within a minimum of space.

The device according to FIGS. 5 and 5a is provided with an inductive concentrator which comprises. a primary high-frequency winding 3 and the concentrator Winding 21 proper. The concentrator winding 21 is formed as a metal body or shell which has one interrupting slot, as shown at 21a. The focus inductor or concentrator 21 is mounted on the jacket 5 and is insulated therefrom by an insulating body 2.0 which also acts as a seal. It is preferable in this case to make the porous cylinder 400 as well as the jacket 5 of insulating material at least in the immediate vicinity of the inductive heating device. The symmetry axes of inductor 21 and walls 5 and 400 preferably intersect at right angles.

The device of FIGS. 5 and 5a is particularly intended for welding. It concentrates the welding heat upon a local area of the workpiece and thus requires that the workpiece be slowly turned in front of the inductor so that a closed welding seam is produced when a single revolution is completed, the turning motion being indicated in FIG. 5 by an arrow 22. The device facilitates the production of the desired welding temperature within a very limited area of the workpiece, while requiring relatively small energy for this purpose.

It will be understood that such a device is also suitable for severing a rod or tube material by melting, or to melt special metal elements in a crucible. Devices of the type described are also applicable for performing cruciblefree, floating zone melting operations on metals, and semi-conductors such as silicon, during which the material may be levitated by the inductive devices knownand used for such purposes, or by surface tension and adhesion to adjoining solid rod portions.

While the devices described above with reference to the drawing are distinguished by their small size, it will further be understood that, depending upon the purposes to be served and depending upon the available supply of high-frequency current, the devices may be given any desired greater dimensions.

1 Other modifications, all in accordance with the essential features of my invention and within the scope of the claims annexed hereto, will be available or obvious to those skilled in the art, upon a study of this disclosure.

I claim:

1. An induction device for heating electrically conducting material in a protective-gas atmosphere in a processing space, comprising inner and outer mutually spaced tubular bodies forming the processing space within the inner tubular body and an interstitial space between each other, an intake for protective gas connected with said interstitial space, the inner tubular body being gas-porous so that when in operation protective gas can enter through the pores into the processing space within the inner tubular member, and electric conductor means for application of high-frequency induction current to said processing space.

2. An induction device for heating electrically conducting material in a protective-gas atmosphere in a processing space, comprising inner and outer mutually spaced tubular bodies, an intake for protective gas communicating with the interstitial space between the tubular bodies, the inner tubular body being gas-porous so that when in operation protective gas can enter into the processing space within the inner tubular member, and electric conductor means for application of high-frequency induction current to said processing space, the inner tubular member being at least partially of electrically non-conducting material, said electric conductor means including an electro-conductive Winding within said inner tubular member, said electro-conductive winding being at least in part supported by said electrically non-conducting material.

3. An induction device for heating electrically conducting material in a protective-gas atmosphere in a processing space, comprising inner and outer mutually spaced tubular bodies, an intake for protective gas communicating with the interstitial space between the tubular bodies, the inner tubular body being gas-porous so that when in operation protective gas can enter into the processing space within the inner tubular member, and electric conductor means for application of high-frequency induction current to said processing space, and structure providing a coaxial extension of the processing space, said structure providing inner and outer spaced tubular body portions, the inner tubular body portion being gas-porous, and an intake for protective, temperature modifying gas communicating with the interstitial space between said body portion, said structure providing supplemental processing space.

4. An induction device for heating electrically conducting material in a protective-gas atmosphere in a processing space, comprising inner and outer mutually spaced tubular structures, an intake for protective gas communicating with the interstitial space between the tubular structures, the inner tubular structure being at least partially electrically non-conductive and being gas-porous so that when in operation protective gas can enter into the processing space within the inner tubular member, and electric conductor means for application of high-frequency induction current to said processing space, said electric conductor means comprising an inductor winding disposed externally about and in electrical-1y insulated relation to the outer tubular body, the latter body being comprised of electro-conductive material and having an electro-conductive portion extending inwardly of the inner tubular member, into said processing space, and serving as electric energy concentrator. 4

5. An induction device for heating electrically conducting material in a protective-gas atmosphere in a processing space, comprising inner and outer mutually spaced tubular structures, an intake for protective gas communicating with the interstitial space between the tubular structures, the inner tubular structure being at least partially electrically non-conductive and being gas-porous so that when in operation protective gas can enter into the processing space within the inner tubular member, and electric conductor means for application of high-frequency induction current to said processing space, said electric conductor means comprising an inductor winding disposed externally about and in electrically insulated relation to the outer tubular body, the latter body being comprised of electro-conductive material and having an electro-conductive portion extending inwardly of the inner tubular member into said processing space, said portion comprising an annular flange serving as electric energy concentrator and providing a bore in which the material being heated can be located, the flange being located intermediate the ends of the inner tubular structure.

6. An induction device for heating electrically conducting material in a protective-gas atmosphere in a processing space, comprising inner and outer mutually spaced tubular structures, an intake for protective gas communicating with the interstitial space between the tubular structures, the inner tubular structure being at least partially electrically non-conductive and being gas-porous so that when in operation protective gas can enter into the processing space within the inner tubular member, and electric conductor means for application of high-frequency induction current to said processing space, said electric conductor means comprising an inductor winding disposed externally about and in electrically insulated relation to the outer tubular body, the latter body being comprised of electro-conductive material and having an electro-conductive portion extending inwardly of the inner tubular member, into said processing space, said portion comprising an annular flange serving as electric energy concentrator and providing a bore in which the material being heated can be located, the flange being located intermediate the ends of the inner tubular structure, the opposite ends of the tubular structures being provided with cover means, said cover means having apertures in coaxial alignment with said bore, for passage of the material processed, the gas flowing within the interstitial space above and below said flange and flowing out through at least one of the apertures.

7. An induction device for heating electrically conducting material in a protective-gas atmosphere in a processing space, comprising inner and outer mutually spaced tubular bodies, an intake for protective gas communicating with the interstitial space between the tubular bodies, the inner tubular body being gas-porous so that when in operation protective gas can enter into the processing space within the inner tubular member, and electric conductor means for application of high-frequency induction current to said processing space, said electric conductor means comprising a primary winding and an electrically conductive focus inductor shell, the inductor shell having a tapering portion facing the processing space, the axis of the inductor being angularly disposed with relation to the axes of said tubular bodies and extending through said bodies in gas sealed relation and in electrically insulated relation thereto.

8. The apparatus defined in claim 7, the axis of the inductor and the axes of the tubular bodies intersecting at right angles.

9. An induction device for heating electrically conducting material in a protective-gas atmosphere in a processing space, comprising inner and outer mutually spaced tubular bodies, an intake for protective-gas communicating with the interstitial space between the tubular bodies, the inner tubular body being gas-porous so that when in Toperation protective gas can enter into the processing space within the inner tubular member, and electric conductor means for application of high-frequency induction current to said processing space, said electric conductor means comprising a primary winding and an electrically conductive focus inductor shell, the inductor shell having a tapering portion facing the processing space, the axis of the inductor being angularly disposed with relation to the axes of said tubular bodies and extending through 5 said bodies in gas sealed relation thereto, the tubular members being of insulating material at least in the portion contiguous to said shell.

References Cited'in the file of this patent UNITED STATES PATENTS 2,649,527 Chapman et al. Aug. 18, 1953 

